Thanks very much Interceptor121. I have been watching your videos and reading your blog with great interest. Lots of information to take in, especially as I don't have the camera in my hands yet.

I did notice occasional vignetting (e.g. top left at 3:50) and occasional soft corners in your first video. Also quite a lot of blown-out highlights in the macro shots. On the other hand some nice magnification on the nudi at 4:41 and the pygmy seahorse 4:50. Which diopter combination did you use for that? And which lens caused the vignetting?

The vignetting is given by the red filter I am using a lens not designed for 28mm which works well without filter but once I added the filter on I had sometime some issues in pushing it in correctly. So it is not systematic but more user error. I have changed the rubber ring on the lens to allow the filter to sit deeper. The soft corners are a depth of field issue, I have seen videos of other people with the 'recommended' lens and still they have soft corners. To me this is because visibility was poor and I had to choose if I was closing the aperture and raising the ISO or leaving a wide aperture and keep noise low. I chose to keep noise low so it is not the lens is the camera.
For the Pygmy I used one or two diopters with 6 or 12 power.
Can you tell me where you see the blown highlights? Are you referring to the night dive?

The lenses I use are in the details of each video they are all Inon

This is the clip of the second part of the trip by then I had worked out what to do with the filter :-)

Thanks Interceptor121. The blown out highlights I referred to were mostly in the night dive video, for example the hermit crab shall at 0:42, the crab at 1:45, or the reef surrounding the ghost pipefishes at 4:20. In the first video I noticed it in the pygmy seahorse's head at 6:00. I realise some of this is unavoidable if you want to see detail in the dark areas, but the handling of it seemed very harsh and "high-contrast". Maybe it's partly a lighting issue. Dimmer lights may help?

Anyway I have now found all those RX100 threads in the Consumer Digicams/Housings forum so I will work my way through them and probably take further discussion over there.

The super macro parts can't be avoided. Consider that no video rig will ever shoot with that level of magnification to balance the image you need to step back and have it smaller

For the night dive I use the camera program mode usually in spot metering as my main concern is the subject not the surroundings. As the RX100 lacks depth of field I need to pump up the lights until I get F8 or smaller aperture. This creates issues with the surroundings and with objects that are white especially when part of the subject is dark (black fish on white sand) again in some cases these could be fixed with manual exposure however considering the shutter speed and the ISO are pretty much fixed once you reach F11 you are pretty much done and sometimes this is not sufficient either

Re. the exposure, I understand Interceptor. I think I would try and go for a lower ISO in some of those situations, then have more chance of retrieving highlight detail in post, while pumping up the midtones/shadows. What do you mean by "pretty much fixed"?

Re. soft corners, am I right in thinking that there is currently no known wide adaptor that gives sharp corners with the Nauticam?

Re. the exposure, I understand Interceptor. I think I would try and go for a lower ISO in some of those situations, then have more chance of retrieving highlight detail in post, while pumping up the midtones/shadows. What do you mean by "pretty much fixed"?

Re. soft corners, am I right in thinking that there is currently no known wide adaptor that gives sharp corners with the Nauticam?

The lowest ISO for the Rx100 in video is 125. I had a Sanyo before with lowest ISO of 50. So all you can do is to close apertureRe wide lens that is a good question would love to make some tests. Lenses with domes with fisheye view seem to perform best. Flat lenses need testing unfortunately I can't buy 2-3 lenses just to try out. Just today am going to out the rx100 in the bathtub and try some shots with slates to see what is actually happening however in still mode the lens is 28mm whilst in video is 33 due to cropping for stabilisation so I will have vignetting in still or I will have to zoom which is not really the same in terms of chromatic aberration and sharpnessI will keep you posted

The lowest ISO for the Rx100 in video is 125. I had a Sanyo before with lowest ISO of 50. So all you can do is to close aperture

Damn that large sensor! A faster shutter is not the end of the world on a lot of macro, especially fairly static stuff like nudibranchs. Can look too stuttery with something like a fast swimming juvenile clownfish though.

Nick. I have done some tests in the bathtub so the story is pretty much like this
Soft corners: if I fill the lens with a slate the image is sharp from f4 and smaller, regardless of what lens I have. This is because of sensor size. I guess a video camera with a 1/3" like yours will always be sharper at lower apertures. However the Sony really has very low level of noise so it compensates with image quality and higher equivalent ISO. This is just a wide angle issue when you have subject in focus at a certain distance and corners much closer or further away
Chromatic aberration: I have dome other checks and there is a little bit of fringing in corners however you need to super zoom to actually see it

All in all not bad for a compact camera. I have also tried with a fisheye lens the corners are sharper however things look to tiny and I can't use a filter so no go

Nick I looked into the original files and the harsh highlights on the hermit crab are because I shot it in Program mode. I think if I had done it in aperture priority there would have been less issues. Camera set the ISO to the minimum

Thanks for all that Interceptor. I read your blog. I am getting a little bit lost with all these different Inon numbers, so I need to take some time to familiarise myself with them all. If you were buying from scratch for the Nauticam housing, would you recommend another wide adaptor over the Inon UWL-H100 for someone who doesn't need super-wide? (I think 100 degrees would be enough for me)

Nick your video is superb and I would never suggest the RX100 can get exactly there however if you want to have a play with it underwater starting from scratch I would get the LD bayonet adaptor and an Inon UWLH-100 28LD. I would not recommend the M67 screw type because the RX100 also need a diopter for macro (Inon UCL165LD) and you would find difficult to screw and unscrew a lens that is 320 grams in water

For what concerns angle of coverage 100 diagonal that is around 90 horizontal is good otherwise things look too tiny. I am only planning to use the fisheye for photos not for video as I don't have lights to cover such angle, actually they don't exist!

The inon gives you the additional advantage to add a dome later should you wish so, but I doubt for video a dome is really needed except whales and similar

I wasn't really thinking this would be my longterm primary rig but something to supplement it.

Good point about getting a bayonet instead of screwing the UWLH-100 in. I'm wondering about a way to have a UWLH-100 with blue water CC filter interchangeable with a Subsee +10 underwater. I see there is the Saga Dive Dual Flip that I suppose could hold the Subsee and the CC filter, but that doesn't really help if one wants to use the wide lens and the CC filter together. Any ideas?

The Inon is 326 grams in water and needs to be really close to the port, a flip holder will not work with a wide angle lens as it will give soft corners and plenty of chromatic aberration

Take also into account that a +10 diopter is only good for super-super macro so you may want to consider a +5 or +6 (there is a post about macro on my blog with more details)

The solution I adopt is to get a push on filter for the wide angle lens (deeproof makes one for the UWLH-100 and you can also try an ikelite with a lanyard) and use a bayonet diopter that can be stacked. With Inon diopters you can get an UCL165LD that is +6 and add another +3 or +6 on top adding another diopter with M67 mount.
With a bayonet caddy placed on an arm you can then switch lenses safely in water